hg: note that islocal only accepts paths pointing to repos

hg.islocal doesn't work for paths pointing to non-repos, such as patch files.

mercurial/hg.py

@@ -82,7 +82,7 b' def _peerlookup(path):'
         return thing
 
 def islocal(repo):
-    '''return true if repo or path is local'''
+    '''return true if repo (or path pointing to repo) is local'''
     if isinstance(repo, str):
         try:
             return _peerlookup(repo).islocal(repo)